1. Field of the Invention
The present invention generally relates to elastomeric tubing, and more particularly to a device and method for securing such tubing around electrical splices and terminals in order to insulate or identify them.
2. Description of the Prior Art
Elastic tubes formed from synthetic or natural materials are commonly used in the electronics industry to facilitate connection of wiring and component parts. The present invention relates to two such applications, namely, insulating electrical splices, and color-coding terminal connectors.
With respect to cable splices, two different kinds of tubing are typically used, viz., heat shrink (thermoplastic) tubing and cold shrink (pre-stretched) tubing. In either case, the tube is attached to the splice by first inserting an end of one of the cables through the tube, performing the splice, and shifting the tube over the splice. With heat shrink tubing, a heat source is then applied, and the tube shrinks around the splice, thereby insulating it. In the case of cold shrink tubing, the tube is pre-stretched over a collapsible core. It is placed over one of the cables in this condition and, after the splice is completed, the tubing is positioned over the splice and the core removed, and the tube shrinks to its relaxed state.
In regard to terminal connectors, it is often useful or necessary to label or otherwise identify terminal connections of interconnected electrical systems. The use of cold shrink tubing in this application is exceedingly difficult since the dimensions involved are particularly small (around 2 millimeter inner tube diameter for most wires) and it is not economically feasible to fabricate collapsible cores which can fit into such a small tube. Accordingly, the technique has heretofore been limited to the use of heat shrink tubing only. This is performed in a manner similar to that described above with respect to cable splices, i.e., insertion of the terminal through the heat shrink tube, and application of a heat source. The color of the tube may then be used to identify the terminal.
The foregoing techniques have several disadvantages. First of all, the use of heat shrink material is more time consuming than the use of cold shrink tubing. Heat shrink tubing also requires a heat source, such as an infrared heater or hot-air gun. Elastomeric tubing, on the other hand, requires provision of the tubing in a pre-stretched state with the collapsible core in place (this process cannot be performed in the field), which also increases expense. Finally, as noted above, cold shrink tubing has proved impossible to use with small terminal connections. It would, therefore, be desirable and advantageous to devise a tool which would facilitate placement, about a terminal connector or cable, of elastomeric tubing which is not pre-stretched and therefore requires no collapsible core.
The closest prior art to such a device is probably a group of plier-like tools used to expand elastic rings. Variations of these tools are described in the following U.S. Pat. Nos.
______________________________________ U.S. Pat. No. Inventor ______________________________________ 1,362,308 F. Heaton 1,683,119 C. Ziegler 2,447,474 A. Hammond 2,582,640 C. Maddox 4,261,089 G. Taylor ______________________________________
The common design characteristic of these devices is the provision of studs or prongs which are passed through an elastic ring and forced apart. The tools disclosed in these patents, however, are unsatisfactory for the stated purpose of this invention, primarily because they are designed to expand rings rather than elongated tubes. For example, the Heaton patent notes (col. 3, 1. 7) that knobs on the end of the expanding lugs prevent the lugs from slipping out of the elastic ring. If used with elastic tubing, this feature would have the undesirable consequence of precluding removal of the lugs from the tube. In other words, these devices may be used to expand tubing, but they cannot be withdrawn from the tubing after a cable or wire has been inserted therein.
Accordingly, the primary object of the present invention is to provide a device for expanding elastomeric tubing.
Another object of the invention is to provide such a device which may be used to apply elastomeric tubing to electrical splices and terminal connectors.
Still another object of the invention is to provide such a device which minimizes friction in applying the tubing to the splice or terminal.
Yet another object of the invention is to provide specialized tips for such a device which may be used to apply adhesive or other sealing compounds around the splice.